Adjustable chairs are well known in the art. In fact, adjustable office seating has now reached a high level of sophistication and maturity. Elements of contemporary ergonomic chairs have been in use for centuries and technological developments can be seen as early as the late 19th century when, for example, innovators focused on improving the back and forth rocking movement possible in chairs. Exemplary patents include U.S. Pat. No. 273,630 to Stevens, and U.S. Pat. No. 317,933 to Doubler. A more involved design is shown in U.S. Pat. No. 1,555,689 to Miller, and early ergonomic rocking designs are seen in U.S. Pat. No. 5,603,551 to Sheehand, and U.S. Pat. No. 5,048,893 to Cowan et al.
Efforts at developing a more practical back and forth tilting action were focused largely on office chairs, in which hinged and tilting seat posts were provided. Illustrative examples of the evolving apparatus are shown in U.S. Pat. No. 3,446,532 to Cramer; U.S. Pat. No. 3,712,666 to Stoll; U.S. Pat. No. 4,979,778 to Shields; and U.S. Pat. No. 5,716,099 to McDiarmid. These patents show increasingly elegant designs for a hinged seat post.
A more challenging aspect in developing truly ergonomic chairs has been in synchronizing, coordinating, and integrating back rest movement with seat plate movement without sacrificing comfort or allowing for dangerous or otherwise awkward seating positions. However, this feature, too, has undergone considerable development in recent years, as illustrated in the following: U.S. Pat. No. 4,451,085 to Franck et al; U.S. Pat. No. 5,810,440 to Unwalla; U.S. Pat. No. 5,826,940 to Hodgdon; U.S. Pat. No. 6,000,755 to Uhlenbrock; and U.S. Pat. No. 6,109,694 to Kurtz.
As an appreciation of the need to provide workers with an ergonomically advantageous workplace has increased, office seating technology has advanced considerably. The past five years has seen a number of significant advances in ergonomic seating that integrates a number of static elements, adjustment features, and dynamic synchronous movement. Those most relevant to a consideration of the present invention are shown in the following references:
U.S. Pat. No. 6,086,153, to Heidmann et al, which discloses a chair, which includes a base assembly with a control housing having opposing side flanges and a side pivot, a back pivoted to the base assembly for movement between upright and reclined positions, and a seat operably supported on the base assembly and connected to the back for coordinated synchronous movement with the back. An energy mechanism biases the back toward the upright position. The energy mechanism includes an extendable/compressible spring positioned transversely in the control housing with one end supported on one of the side flanges, and further includes a lever pivoted to the side pivot and having a spring-engaging portion engaging a free end of the spring and also having a seat-biasing portion operably connected to the seat. The side pivot, the spring-engaging portion, and the seat-biasing portion are spaced from each other and arranged so that the spring biases the lever about a fulcrum located generally at the side pivot to bias the back toward the upright position.
U.S. Pat. No. 6,386,634 to Stumpf et al., teaches an office chair having a seat, a back and a pair of armrests. In its primary aspects, the chair includes a linkage assembly that allows the seat and back to tilt downwardly and rearwardly and to allow pivotal movement of the seat about a pivot axis in substantial alignment with the hip joints of a user. This is intended to inhibit shear forces from pulling the clothing on the body of a user. The linkage assembly may also adapted to allow the seat and back to tilt downwardly and rearwardly such that the seat pivots about an effective pivot point at substantially the ankle of a user having feet resting on a floor.
U.S. patent application Ser. No. 2003/0001420 by Koepke et al., teaches an ergonomic chair that purportedly incorporates synchronous tilt of back and seat; tilt limit control; separate seat adjustment; arm adjustment; adjustable lumbar support; cushion airflow; mesh attachment and modular base frame assembly. The chair comprises a four bar linkage system causing the seat rear to elevate as the back is reclined. A tilt limit restricts the degree of chair back tilt to a predetermined reclined position with manual movement of a lever. Horizontal positioning of the chair seat cushion is accomplished with a positive locking device. Height and pivot adjustable chair arms are actuated with buttons or rotation. A height adjustable lumbar support is provided, with adjustments requiring no screws or adjustment knobs and without the need of direct contact of the lumbar support with the back of the user.
U.S. Pat. No. 6,698,833 to Ball et al., describes an adjustable office chair with a base having a control assembly operably supporting a seat assembly and also a back assembly for movement about a seat tilt axis and a back tilt axis, respectively. The back assembly includes a flexible sheet hung tightly and hanging down from the upper corners of the back support structure. The lower portion of the flexible sheet is coupled to the back support structure by a tensioner for holding the lower portion rearwardly. A vertically adjustable lumbar mechanism is supported on the back support structure and biases an intermediate portion of the flexible sheet forwardly to both form the intermediate portion into a forwardly convex shape for postural lumbar support and also to tension the flexible sheet.
U.S. patent application Ser. No. 2002/0149247 by Diffrient, discloses an occupant-weight-operated chair having a seat and a back mounted upon support structure, such as a caster-mounted pedestal. The back reclines relative to the seat, and the structure of the chair, and the relationship of the components, is such that as the back is reclined the entire seat raises against the weight of the occupant. Accordingly, the occupant's weight loads the chair mechanism, and the force required to recline the back is substantially uniform throughout the back-reclining range of movement. The back of the chair is attached to the rear of the seat region so that reclining the back raises the elevation of the seat rear region against the occupant's weight. The combination of the upward movement of the chair seat in conjunction with the reclining rotation of the chair back simulates the movement of the user's torso about the user's hip joint as the user reclines.
The foregoing patents reflect the current state of the art of which the present inventor is aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicant's acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.